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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * particular file as subject to the "Classpath" exception as provided
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
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 *
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package java.util.function;

import java.util.Objects;

/**
 * An operation on a {@code double} operand yielding a {@code double}
 * result. This is the primitive type specialization of {@link UnaryOperator}
 * for {@code double}.
 *
 * @see UnaryOperator
 * @since 1.8
 */
@FunctionalInterface
public interface DoubleUnaryOperator {

    /**
     * Returns the {@code double} result of the operation upon the
     * {@code double} operand.
     *
     * @param operand the operand value
     * @return the operation result value
     */
    double applyAsDouble(double operand);

    /**
     * Compose a new function which applies the provided function followed by
     * this function.  If either function throws an exception, it is relayed
     * to the caller.
     *
     * @param before An additional function to be applied before this function
     * is applied
     * @return A function which performs the provided function followed by this
     * function
     * @throws NullPointerException if before is null
     */
    default DoubleUnaryOperator compose(DoubleUnaryOperator before) {
        Objects.requireNonNull(before);
        return (double v) -> applyAsDouble(before.applyAsDouble(v));
    }

    /**
     * Compose a new function which applies this function followed by the
     * provided function.  If either function throws an exception, it is relayed
     * to the caller.
     *
     * @param after An additional function to be applied after this function is
     * applied
     * @return A function which performs this function followed by the provided
     * function followed
     * @throws NullPointerException if after is null
     */
    default DoubleUnaryOperator andThen(DoubleUnaryOperator after) {
        Objects.requireNonNull(after);
        return (double t) -> after.applyAsDouble(applyAsDouble(t));
    }

    /**
     * Returns a unary operator that provides its input value as the result.
     *
     * @return a unary operator that provides its input value as the result
     */
    static DoubleUnaryOperator identity() {
        return t -> t;
    }
}